This application claims the benefit of Korean Application No. 2001-70014, filed Nov. 12, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a paper cassette holding printing paper and mounted in a printer body of a printer, and more particularly, to a paper cassette having a shock absorbing unit absorbing a shock generated from a supporting plate of the paper cassette which moves at a high speed or at a low speed.
2. Description of the Related Art
Generally, a printing device like a copier and a laser printer has a paper cassette holding printing paper and mounted in a body of the printing device.
FIG. 1 is a sectional view schematically showing a typical example of the paper cassette. Referring to FIG. 1, the paper cassette includes a cassette body 10, a paper supporting plate 11 movably disposed within the cassette body 10 to be raised, lowered, and pivoted, a spring 12 elastically supporting the supporting plate 11, a finger member 13 limiting a range of a rising movement of the supporting plate 11 and also separating the printing paper from a stack of the paper cassette sheet by sheet, and a locking unit 14 securing the supporting plate 11 to a bottom of the cassette body 10.
One end of the supporting plate 11 is connected to the cassette body 10 by a hinge 15 and accordingly hinged on the hinge 15.
In order to stack the printing paper in the cassette body 10 of the paper cassette constructed as above, a user of the printing device pushes the supporting plate 11 downward to the bottom of the cassette body 10. Accordingly, the supporting plate 11 is pushed to be in tight contact with the bottom of the cassette body 10 and maintained in a horizontal state as indicated by two-dotted lines of FIG. 1 by the locking unit 14. In the horizontal state of the supporting plate 11, the user stacks the printing paper on the supporting plate 11 and then reconnects the paper cassette to the body of the printing device by sliding the paper cassette into the body of the printing device. As the cassette body 11 is re-connected to the body of the printing device, the locking unit 14 is interfered with by inner walls of the body of the printing device to be unlocked.
Being unlocked, the supporting plate 11 springs up by elasticity (an elastic force) of the spring 12. A speed with which the supporting plate 11 springs up is inversely-proportional to an amount of the printing paper stacked on the supporting plate 11 of the paper cassette. In other words, when there is a large amount of the printing paper stacked on the supporting plate 11, the speed of a jumping movement of the supporting plate 11 is relatively reduced by a weight of the printing paper.
When there is a small amount of the printing paper on the supporting plate 11, the supporting plate 11 springs up quickly and collides against the finger member 13 with an intense shock. Here, due to the intense shock, some sheets of the printing paper may be slid (released) from the finger member 13, and sometimes there is a considerably high noise occurring from the supporting plate 11 and the finger member 13.
In an attempt to solve the above-described problem, a suggestion has been made that the locking unit 14 should be removed from the paper cassette. In this case, the user has to stack the printing paper in a state that the supporting plate 10 is at a highest point where the supporting plate 10 has sprung up by the elasticity of the spring 12. Otherwise, the user has to stack the printing paper with one hand while pushing down the supporting plate 10 with the other hand. This is very inconvenient for the user to stack the printing paper in the paper cassette, and this situation becomes even worse when the user has to align sides of the paper with sidewalls of the paper cassette.
The present invention has been made to overcome the above and other problems of the related art, and accordingly, it is an object of the present invention to provide a paper cassette adapted for use in a printing device and having an improved structure for a user to easily stack printing paper without noise.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The above and other objects are achieved by providing a paper cassette for use in a printing device according to an embodiment of the present invention. The paper cassette includes a cassette body connected to a body of the printing device, a supporting plate having a first end pivotally disposed in the cassette body to support printing paper, a spring elastically supporting a lower side of the supporting plate relative to a bottom of the cassette body, a finger member disposed on the cassette body to limit a rising height of the supporting plate and separating the printing paper sheet by sheet, and a shock absorbing unit guiding a rising and lowering movement of the supporting plate and lessening (absorbing) a shock exerted on the finger member by reducing a rising speed of the supporting plate when the supporting plate stacked with the printing paper is raised from a lowered state by the spring.
The shock absorbing unit includes a guide pin formed on a second end of the supporting plate and a pivot member pivotally disposed on the cassette body. The pivot member includes a first guide rail that simply guides the guide pin, and a second guide rail that guides the guide pin while providing the guide pin with a frictional force so as to reduce a pivotal force of the supporting plate.
The pivot member reciprocates between a first position and a second position so that the first guide rail guides the guide pin when the pivot member is in the first position and the second guide rail guides the guide pin when the pivot member is in the second position. It is possible that the pivot member is moved to the first position when the supporting plate is at the lowered state.
During raising the supporting plate, the guide pin comes into contact with a first interference portion provided at a first entry portion of the first guide rail, and the pivot member is either maintained at the first position or forced to pivot to the second position according to the extent (an amount) of a contact force generated between the guide pin and the first interference portion.
The extent of the contact force is determined according to a rising speed of the supporting plate that is determined according to an amount of the printing paper stacked on the supporting plate. The guide pin is guided from the first entry portion of the first guide rail to a second entry portion of the second guide rail by a guide side connected between the first entry portion of the first guide rail and the second entry portion of the second guide rail.
According to an aspect of the present invention, at least a pair of elastic substances are disposed on an inner side of the second guide rail to provide the frictional force during the movement of the guide pin.
The pair of elastic substances is formed away from the second entry portion of the second guide rail by a distance corresponding to two-thirds of a length of the second guide rail.
A second interference portion protrudes from the second entry portion of the second guide rail to have a predetermined shape to interfere with the guide pin moving into and out of the second guide rail. With the supporting plate being lowered and the guide pin moving out from the second guide rail, the pivot member is forcedly pivoted from the second position to the first position by the contact force at the second interference portion.
According to another aspect of the present invention, a guide unit limits a range of pivotal movement of the pivot member and guiding the pivotal movement of the pivot member. The guide unit includes a third guide rail formed in the pivot member and a securing pin disposed in the cassette body to move along the third guide rail.
According to yet another aspect of the present invention, a locking unit securely locks the supporting plate in a lowered position when the supporting plate is lowered to be in close contact with a bottom of the cassette body, wherein the locking unit is unlocked when the supporting plate is inserted into the body of the printing device.
The above and other objects are also accomplished by providing a paper cassette adapted for use in a printing device according to another embodiment of the present invention. The paper cassette includes a cassette body connected to a body of the printing device a supporting plate movably disposed within the cassette body to be raised and lowered during supporting printing paper, a spring elastically supporting a lower end of the supporting plate relative to a bottom of the cassette body, and a shock absorbing unit guiding a rising and lowering movement of the supporting plate to lessen or absorb a shock by reducing a rising speed of the supporting plate when the supporting plate stacked with the printing paper is raised by the spring, wherein the shock absorbing unit limits a rising height of the supporting plate.
The shock absorbing unit includes a portion defining an opening formed at a first end of the supporting plate, a hinge pin formed on the cassette body to be inserted into the opening and to support the first end of the supporting plate to pivot relative to the cassette body and to horizontally slide by a predetermined distance, a guide pin formed at a second end of the supporting plate, and a guide rail in a shape of an arc and formed in the cassette body to guide the guide pin during the rising and lowering movement of the supporting plate. The guide pin is guided to be in contact with one side of the guide rail by a pressing force of the spring, thereby reducing a rising force of the supporting plate. The opening of the portion may be formed at the cassette body while the hinge pin may be formed in the first end of the supporting plate.
According to still another aspect of the present invention, a frictional force providing unit is formed on one side of the guide rail which is contacted with the guide pin, to selectively provide a frictional force according to a moving position of the guide pin.
The frictional force providing unit includes a curved portion curved-in from the one side of the guide rail to provide the guide pin with the frictional force.
The guide rail is a guide slot integrally formed in an inner side of the cassette body.
According to still yet another aspect of the present invention, a secondary slot is formed in the cassette body in parallel with the guide slot to provide the frictional force by being deformed when the guide pin contacts the one side of the guide slot.